Mobile device front end architecture for time division duplexing

ABSTRACT

A switching circuit for use in a frequency division duplex (FDD) spectrum re-allocated for time division duplex (TDD) applications comprises a first filter configured to filter a TDD receive signal, a duplex filter configured to filter an FDD receive signal, and a plurality of switches configured to route the FDD receive signal from an antenna through the duplex filter to receiver circuitry and to route the TDD receive signal from the antenna through the first filter to the receiver circuitry such that the FDD and TDD receive signals share the FDD spectrum.

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

Any and all applications for which a foreign or domestic priority claimis identified in the Application Data Sheet as filed with the presentapplication are hereby incorporated by reference under 37 CFR 1.57.

BACKGROUND

1. Field of the Invention

The present invention is generally in the field of radio communications,and more particularly, to reallocating of the frequency spectrum.

2. Description of the Related Art

Frequency Division Duplex (FDD) is a method of two-way radiocommunication where devices on one end transmit using one radiofrequency, while devices on the other end transmit using a differentfrequency. This paired unit of radio frequency (RF) spectrum allowssimultaneous two-way communication without interference. For example,this is how most cellular phone networks are designed. Cellular phonestransmit to network towers using one frequency, while network towerstransmit to phones on a different frequency. As data traffic increases,data capacity is limited by the fixed bandwidths of the paired spectrum.

SUMMARY

Systems and methods are disclosed to use a frequency division duplex(FDD) spectrum that is re-allocated for time division duplex (TDD)applications. A switching circuit comprises a first filter configured tofilter a TDD receive signal, a duplex filter configured to filter an FDDreceive signal, and a plurality of switches configured to route the FDDreceive signal from an antenna through the duplex filter to receivercircuitry and to route the TDD receive signal from the antenna throughthe first filter to the receiver circuitry such that the FDD and TDDreceive signals share the FDD spectrum.

In certain embodiments, a switching circuit used in an FDD spectrumre-allocated for TDD application comprises a first filter configured tofilter a TDD receive signal, a duplex filter configured to filter an FDDreceive signal, and a plurality of switches configured to route the FDDreceive signal from an antenna through the duplex filter to receivercircuitry and to route the TDD receive signal from the antenna throughthe first filter to the receiver circuitry, where the FDD and TDDreceive signals share the FDD spectrum.

In an embodiment, the duplex filter includes a surface acoustic wave(SAW) filter. In another embodiment, the switching circuit furthercomprises a second filter configured to filter a TDD transmit signal,where the duplex filter is further configured to filter an FDD transmitsignal. In a further embodiment, the first filter, the second filter,and the duplex filter include bandpass filters. In a yet furtherembodiment, the plurality of switches are further configured to routethe TDD transmit signal from transmitter circuitry through the secondfilter to the antenna, and to route the FDD transmit signal from thetransmitter circuitry through the duplex filter to the antenna, wherethe FDD and TDD transmit signals share a first frequency band of the FDDspectrum.

In another embodiment, the TDD transmit, TDD receive, FDD transmit, andFDD receive signals are radio frequency (RF) signals. In anotherembodiment, a wireless device includes the switching circuit.

According to a number of embodiments, a switching module for use in afrequency division duplex (FDD) spectrum re-allocated for time divisionduplex (TDD) application comprises a switching circuit implemented in afirst semiconductor die, where the switching circuit includes a firstfilter configured to filter a TDD receive signal, a duplex filterconfigured to filter an FDD receive signal, and a plurality of switchesconfigured to route the FDD receive signal from an antenna through theduplex filter to receiver circuitry and to route the TDD receive signalfrom the antenna through the first filter to the receiver circuitry,such that the FDD and TDD receive signals share the FDD spectrum, and atleast one of a prefilter circuit, a post filter circuit, a poweramplifier circuit, a switch circuit, a down converter circuit, and amodulator circuit implemented in a second semiconductor die.

In an embodiment, the duplex filter includes a surface acoustic wave(SAW) filter. In another embodiment, the switching circuit furtherincludes a second filter configured to filter a TDD transmit signal, theduplex filter further configured to filter an FDD transmit signal. In afurther embodiment, the first filter, the second filter, and the duplexfilter include bandpass filters. In a yet further embodiment, theplurality of switches are further configured to route the TDD transmitsignal from transmitter circuitry through the second filter to theantenna and to route the FDD transmit signal from the transmittercircuitry through the duplex filter to the antenna, where the FDD andTDD transmit signals share a first frequency band of the FDD spectrum.

In an embodiment, the duplex filter includes a film bulk acousticresonator (FBAR) filter. In another embodiment, the duplex filterincludes a bulk acoustic wave (BAW) filter. In a further embodiment, awireless device includes the switching module.

In accordance with various embodiments, a wireless device for use in FDDspectrum that is re-allocated for TDD application is disclosed. Thewireless device comprises an antenna configured to receive an RF inputsignal and to transmit an RF output signal, a transmitter configured toprovide the antenna with the RF output signal, where the RF outputsignal is one of a TDD transmit signal and an FDD transmit signal, areceiver configured to amplify the received RF input signal, where thereceived RF input signal being one of a TDD receive signal and an FDDreceive signal, and a switching circuit including a first filterconfigured to filter the TDD receive signal, a duplex filter configuredto filter the FDD receive signal, and a plurality of switches configuredto route the FDD receive signal from the antenna through the duplexfilter to the receiver and to route the TDD receive signal from theantenna through the first filter to the receiver, where the FDD and TDDreceive signals share the FDD spectrum.

In an embodiment, the switching circuit further includes a second filterconfigured to filter the TDD transmit signal, the duplex filter furtherconfigured to filter an FDD transmit signal. In another embodiment, theplurality of switches is further configured to route the TDD transmitsignal from the transmitter through the second filter to the antenna andto route the FDD transmit signal from the transmitter through the duplexfilter to the antenna, where the FDD and TDD transmit signals share afirst frequency band of the FDD spectrum.

In certain other embodiments, a method to transmit and receive FDDsignals and TDD signals in an FDD and TDD shared frequency band isdisclosed. The method comprises routing an FDD receive signal from anantenna to receiver circuitry through a duplex filter configured tofilter the FDD receive signal, and routing a TDD receive signal from theantenna to the receiver circuitry through a first filter configured tofilter the TDD receive signal, the FDD and TDD receive signals sharingan FDD spectrum.

The method further comprises routing an FDD transmit signal from thetransmitter circuitry to the antenna through the duplex filter that isfurther configured to filter the FDD transmit signal. The method furthercomprises routing a TDD transmit signal from the transmitter circuitryto the antenna through a second filter configured to filter the TDDtransmit signal, where the FDD and TDD transmit signals share the FDDspectrum.

In an embodiment, the duplex filter includes a surface acoustic wave(SAW) filter. In another embodiment, the duplex filter is selected fromthe group consisting of a surface acoustic wave (SAW) filter, a filmbulk acoustic resonator (FBAR) filter, and a bulk acoustic wave (BAW)filter.

In accordance with various other embodiments, an FDD paired spectrumre-apportioned for TDD communications comprises a first frequency bandconfigured to operate as a first downlink for FDD RF signals, and asecond frequency band different than the first frequency band, thesecond frequency band including an FDD transmit portion configured tooperate as a first uplink for FDD RF signals, a first TDD portionconfigured to operate as a second uplink and a second downlink for TDDRF signals, and a dual-use portion.

In an embodiment, the dual-use portion of the second frequency band isconfigured to operate as a guard band when signal interference betweenthe FDD transmit portion and the TDD portion is greater than athreshold. In another embodiment, the dual-use portion of the secondfrequency band is further configured to operate as a third uplink forTDD RF signals when the signal interference is less than the threshold.In a further embodiment, the FDD paired spectrum further comprises a gapband configured to operate as a third uplink and a third downlink forTDD RF signals. In a yet further embodiment, the gap band is furtherconfigured to operate as one of a guard band and a fourth uplink for TDDRF signals.

In certain other embodiments, a switching circuit for use in an FDDspectrum re-allocated for time TDD application is disclosed. Theswitching circuit comprises a duplex filter configured to filter RFsignals, and a plurality of switches configured to route an FDD receivesignal from an antenna through the duplex filter to receiver circuitry,to route a TDD receive signal from the antenna through the duplex filterto the receiver circuitry, to route an FDD transmit signal fromtransmitter circuitry through the duplex filter to the antenna, and toroute a TDD transmit signal from the transmitter circuitry through theduplex filter to the antenna, where the FDD transmit signals, the TDDtransmit signals, and the TDD receive signals share a frequency band ofthe FDD spectrum.

According to a number of other embodiments, a switching circuit for usein an FDD spectrum re-allocated for TDD application is disclosed. Theswitching circuit comprises a duplex filter configured to filter RFsignals, and a plurality of switches configured to route an FDD receivesignal from an antenna through the duplex filter to receiver circuitry,to route a TDD receive signal from the antenna through the duplex filterto the receiver circuitry, to route an FDD transmit signal fromtransmitter circuitry through the duplex filter to the antenna, and toroute a TDD transmit signal from the transmitter circuitry through theduplex filter to the antenna, where the FDD receive signals, the TDDtransmit signals, and the TDD receive signals share a frequency band ofthe FDD spectrum.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a frequency division duplex (FDD)paired spectrum, according to certain embodiments.

FIG. 2 illustrates an example of time division duplex (TDD)communication, according to certain embodiments.

FIG. 3 illustrates an example of a re-apportioned FDD TX uplink band ofan FDD paired spectrum for TDD application, according to certainembodiments.

FIG. 4 is a schematic diagram of an embodiment of a switching circuitconfigured to switch the RF transmit signal and the RF receive signalfor use in a re-allocated FDD spectrum for TDD application.

FIG. 5 is a schematic diagram of another embodiment of a switchingcircuit configured to switch the RF transmit signal and the RF receivesignal for use in a re-allocated FDD spectrum for TDD application.

FIG. 6A is a schematic diagram of another embodiment of a switchingcircuit configured to switch the RF transmit signal and the RF receivesignal for use in a re-allocated FDD TX uplink band of FDD pairedspectrum for TDD application.

FIG. 6B is a schematic diagram of another embodiment of a switchingcircuit configured to switch the RF transmit signal and the RF receivesignal for use in a re-allocated FDD RX downlink band of an FDD pairedspectrum for TDD application.

FIG. 6C is a schematic diagram of another embodiment of a switchingcircuit configured to switch the RF transmit signal and the RF receivesignal for use in a re-allocated FDD TX uplink band and a re-apportionedduplex gap band of an FDD paired spectrum for TDD application.

FIG. 6D is a schematic diagram of another embodiment of a switchingcircuit configured to switch the RF transmit signal and the RF receivesignal for use in a re-allocated FDD RX downlink band and are-apportioned duplex gap band of an FDD paired spectrum for TDDapplication.

FIG. 7 illustrates an example of a re-apportioned FDD receive downlinkband of an FDD paired spectrum for TDD application, according to certainembodiments.

FIG. 8 illustrates an example of a re-apportioned duplex gap band of anFDD paired spectrum for TDD application, according to certainembodiments.

FIG. 9A is an exemplary block diagram of a multimode semiconductor dieincluding an embodiment of a switching circuit to implement an FDD andTDD shared band, according to certain embodiments.

FIG. 9B is an exemplary block diagram of a switching circuit set ofhaving a first semiconductor die including an embodiment of filtercircuits and a second semiconductor die including an embodiment of aswitching circuit, according to certain embodiments.

FIG. 9C is an exemplary perspective cut-away view of an embodiment of asurface acoustic wave (SAW) filter, according to certain embodiments.

FIG. 10A is an exemplary block diagram of switching module including themultimode semiconductor die of FIG. 9A, according to certainembodiments.

FIG. 10B is an exemplary block diagram of a switching module includingthe filter and switch semiconductor die of FIG. 9B, according to certainembodiments.

FIG. 10C is an exemplary block diagram of a multi-chip module includinga plurality of SAW filters of FIG. 9C, and the filter and switchsemiconductor die of FIG. 9B, according to certain embodiments.

FIG. 11 is an exemplary block diagram illustrating a simplified wirelessdevice including an embodiment of a switching circuit to implement anFDD and TDD shared band, according to certain embodiments.

DETAILED DESCRIPTION

The features of the systems and methods will now be described withreference to the drawings summarized above. Throughout the drawings,reference numbers are re-used to indicate correspondence betweenreferenced elements. The drawings, associated descriptions, and specificimplementation are provided to illustrate embodiments of the inventionsand not to limit the scope of the disclosure.

FIG. 1 illustrates an example of a frequency division duplex (FDD)paired spectrum 100 comprising an FDD transmit (TX) uplink (UL) 102, aduplex band gap 104, and an FDD receive (RX) downlink (DL) 106. FIG. 1shows transmitting and receiving occurring at approximately the sametime, but at different frequencies. Approximately 90% of existing datatraffic in modern networks is downlink, which uses the FDD RX DL 106 ofthe FDD paired spectrum 100. Yet the paired spectrum 100 allocates halfthe spectrum to uplink (FDD TX UL 102). FDD paired spectrum ties uptransmit-only spectrum when it is needed for receive at the userequipment. Evolving use of the FDD TX UL 102 for dual-use as receivedownlink will be critical for network capacity and bandwidth efficiency.

An alternative to FDD is Time Division Duplex (TDD). TDD is a method fortwo-way communication where mobile devices and base station towers ateach end of a connection “take turns” transmitting on the same channel.In radio networks like cellular phone networks, for example, devicestake turns transmitting on the same radio frequency. FIG. 2 illustratesan example of a TDD spectrum 200, which shows transmitting (TDD TX UL)and receiving (TDD RX DL) occurring at different times using the same orapproximately the same frequency.

Embodiments apportion parts of the established FDD transmit spectrum forTDD application, while providing for legacy FDD user equipment (UE) tocontinue operation while simultaneously supporting TDD transmit andreceive use of the transmit band, so that more receive spectrum can bemade available.

Advantageously, this enables more receive spectrum to be used that iscompatible with existing FDD spectral outlays. Other embodiments makeuse of accurate scheduling of the TDD operation and intelligent feedbackto optimally allocate guard bands when and where needed, depending onthe interference environment. Further embodiments use the guard bandsfor transmitting when needed without coexistence implications.

FIG. 3 illustrates an example of a re-apportioned FDD paired spectrum300 for TDD application in the transmit band. The FDD spectrum 300comprises the FDD RX DL 106 and a re-apportioned or re-farmed FDDtransmit uplink that supports TDD transmit/receive use of the transmitband, indicated herein as FDD TX UL+TDD TX/RX 302 or band 302. Band 302comprises one or more FDD TX bands 304, one or more dual-use bands 306,and one or more TDD RX/TDD TX bands 308.

FDD TX bands 304 are used for FDD transmit. For example, legacy userequipment uses the FDD TX bands 304 for continuous FDD transmissions,just as FDD TX band 102 is used for continuous FDD transmissions.

The TDD TX/TDD RX band 308 is used for TDD transmit and receive. The TDDTX/TDD RX band 308 is synchronized to enable sufficient receiveperformance and to avoid nearby TDD transmissions.

In an embodiment, the TDD TX/TDD RX band 308 can be placed adjacent tothe FDD TX spectrum 304 as long as neighboring FDD user equipment doesnot cause desense or a degradation in sensitivity due to noise sourcesof the TDD user equipment.

Guard bands may enhance coexistence of the FDD TX spectrum and the TDDRX/TDD TX spectrum within the band 302 where nearby user equipment maybe interfering with the receiving. In an embodiment, the dual-use bands306 comprise guard bands. This can be dynamically allocated for spectralefficiency.

In another embodiment, the dual-use bands 306 may be used for TDDtransmitting. In a further embodiment, the dual-use bands 306 may beused for transmitting when TDD transmit is useful or needed, and asguard bands when receive operation required and FDD transmitinterference is present. In an embodiment, the interference can bedetermined by measuring the received signal strength indication (RSSI).In an embodiment, the use of the dual-use bands 306 as either guardbands or TDD transmit is based at least in part on RSSI feedback. In anembodiment, the use of the dual-use bands 306 as either guard bands orTDD transmit bands can be dynamically adjusted if RSSI feedbackindicates interference.

Separation between mobile units yields at least −40 dB isolation userequipment to user equipment (UE-to-UE). In an embodiment, emissionsshould be less than approximately −75 dBm/4.5 MHz from the interferinguser equipment antenna to avoid desense in TDD receive channels. Guardbands 306 and PA linearity can be adjusted as needed to achievesufficient performance.

To utilize the frequency re-allocation described above, the front-endmodule of a wireless communication device, such as a cell phone and thelike, comprises a switching and signal conditioning/filtering circuit todirect the RF transmit signal from the power amplifier through theselected one of the FDD transmit circuitry and the TDD transmitcircuitry to an antenna for transmission. The switching and filteringcircuit further directs the RF receive signal received by the antennathrough the selected one of the FDD receive circuitry and the TDDreceive circuitry for baseband processing.

FIG. 4 is a schematic diagram of an embodiment of a switching andfiltering circuit 400 configured to switch the RF transmit signal andthe RF receive signal for use in a re-allocated FDD spectrum for TDDapplication.

The RF transmit signal, indicated as FDD/TDD RF_(TX) in FIG. 4, is sentfrom transmitter circuitry to a power amplifier 402. The power amplifier402 receives the FDD/TDD RF transmit signal and amplifies the signal fortransmission. The FDD/TDD RF transmit signal may be provided for TDDtransmission or FDD transmission, depending on the arrangement of thepaired spectrum 300. In an embodiment, the FDD/TDD RF transmit signalcomprises a high band transmit signal. A matching circuit 404 receivesthe amplified RF transmit signal from the power amplifier 402 andprovides impedance matching for the transmit signal.

The switching circuit 400 receives the impedance matched FDD/TDD RFtransmit signal from the matching circuit 404 and routes the FDD/TDD RFtransmit signal through the appropriate filter to an FDD/TDD antenna 450for TDD transmission or FDD transmission, depending on the arrangementof the paired spectrum 300.

Further, the switching circuit 400 receives an RF receive signal,indicated as FDD/TDD RF_(RX), from the FDD/TDD antenna 450 and routesthe FDD/TDD RF receive signal through the appropriate filter to receivercircuitry for subsequent downconversion and baseband processing. TheFDD/TDD RF receive signal may be received as an FDD signal or a TDDsignal, depending on the arrangement of the paired spectrum 300.

The switching circuit 400 comprises a first or TX select switch 406, asecond or RX select switch or 408, a third switch or antenna switchingmodule 410, a plurality of FDD duplex filters 412, 414, 416, a pluralityof TDD receive filters 422, 424, 426, and a plurality of TDD transmitfilters 432, 434, 436.

The FDD duplex filters 412, 414, 416, for example, can be configured tofilter transmit and receive FDD RF signals in radio devices, where thetransmission and the reception are made at different frequencies via thesame antenna. Typically, a duplex filter is a three-port circuit elementcomprising transmitter port, a receiver port, and an antenna port. An RFsignal supplied to the transmitter port at the transmit frequency seesthe signal path towards the receiver port as a high impedance, so thatthe radio power is not substantially directed to the receiver port, butit is directed through the antenna port to the antenna, where it isradiated as a RF signal to the environment. Correspondingly, an RFsignal received through the antenna and the antenna port at the receivefrequency sees the transmitter port as a high impedance, so that it isdirected to the receiver port and further to the receiver sections ofthe radio device. The function of the duplex filter is generally basedon different frequency response characteristics of the filtercomponents. In an embodiment, the FDD duplex filters 412, 414, 416 eachfurther comprise a transmit filter and a receive filter. In anembodiment, the transmit filters and the receive filters comprisebandpass filters. Further combinations of these TX and RX bands can belogically extended to gang multiple TX and RX filters together toward asingle antenna port as well.

The TDD receive filters 422, 424, 426 are configured to filter TDD RFreceive signals from the FDD/TDD antenna 450. The outputs of the TDDreceive filters 422, 424, 426 are routed to receiver portions of theradio device for further processing. In an embodiment, the TDD receivefilters 422, 424, 426 comprise bandpass filters. These filters may alsobe similarly ganged together to share a common connection, but stillsignal condition a dedicated RX path on the way to the transceiver andradio downconversion and baseband processing.

The TDD transmit filters 432, 434, 436 are configured to filter TDD RFtransmit signals from the matching circuit 404. The outputs of the TDDRF transmit filters 432, 434, 436 are routed to the FDD/TDD antenna 450for transmission. In an embodiment, the TDD transmit filters 432, 434,436 comprise bandpass filters. These filters may also be similarlyganged together to share a common connection, but still signal conditiona dedicated TX path on the way to the antenna.

In the example illustrated in FIG. 4, the plurality of FDD duplexfilters comprises three filters, the plurality of TDD receive filterscomprises three filters, and the plurality of TDD transmit filterscomprises three filters. In other embodiments, there may be more or lessthan three FDD duplex filters, more or less than three TDD receivefilters, and more or less than three TDD transmit filters, and combinedin various ways depending on the frequency band allocation for FDDsignals and the time slot allocation for TDD signals in the pairedspectrum 300.

In the embodiment illustrated in FIG. 4, the first switch 406 comprisesa single pole 6 throw (SP6T) switch where three of the throwselectrically connect to a transmitter port of a corresponding one of theFDD duplex filters 412, 414, 416, three of the throws electricallyconnect to an input of a corresponding TDD transmit filter 432, 434,436, and the pole electrically connects to the output of the matchingcircuit 404. The position of the first switch 406 is controlled by atleast one signal from a baseband subsystem that includes a processor andis based at least in part on the arrangement of the paired spectrum 300.

The first switch 406 receives the output of the matching circuit 404 androutes the FDD/TDD RF transmit signal to the appropriate transmitfilter. When the FDD/TDD RF transmit signal comprises an FDD RF transmitsignal, the first switch 406 routes the FDD RF transmit signal to thetransmitter port of the selected one of the FDD duplex filters 412, 414,416 where the transmit filter of the selected one of the FDD duplexfilters 412, 414, 416 filters the FDD RF transmit signal.

When the FDD/TDD RF transmit signal comprises a TDD RF transmit signal,the first switch 406 routes the TDD RF transmit signal to the input of aselected one of the TDD transmit filters 432, 434, 436 where theselected one of the TDD transmit filters 432, 434, 436 filters the TDDRF transmit signal. As indicated above, the position of the first switch406 is controlled by the at least one signal from the basebandsubsystem. Thus, at least one signal from the baseband subsystemcontrols the selection of the TDD transmit filters 432, 434, 436 and theselection is based at least in part on the arrangement of the pairedspectrum 300.

The third switch 410 routes the FDD/TDD RF transmit signal from theselected filter 412, 414, 416 432, 434, 436 to the FDD/TDD antenna 450for transmission. In the embodiment illustrated in FIG. 4, the thirdswitch 410 comprises a single pole 9 throw (SP9T) switch where three ofthe throws electrically connect to an output of a corresponding TDDtransmit filter 432, 434, 436, three of the throws electrically connectto a corresponding antenna port of the FDD duplex filters 412, 414, 416,three of the throws electrically connect to an input of a correspondingTDD receive filter 422, 424, 426, and the pole electrically connects toantenna circuitry including the FDD/TDD antenna 450. The position of thethird switch 410 is controlled by at least one signal from the basebandsubsystem that includes the processor and is based at least in part onthe arrangement of the paired spectrum 300. When the switching circuit400 is configured to transmit, the third switch 410 is configured toelectrically connect a selected one of the outputs of the filters 412,414, 416, 432, 434, 436 to the FDD/TDD antenna 450.

As described above, the FDD/TDD antenna 450 is also configured toreceive RF signals. When the switching circuit 400 is configured toreceive, the FDD/TDD antenna 450 receives the FDD/TDD RF receive signal.The third switch 410 routes the FDD/TDD RF receive signal to theappropriate receive filter. For example, when the FDD/TDD RF receivesignal comprises an FDD RF receive signal, the third switch 410 routesthe FDD RF receive signal to the antenna port of the selected one of theFDD duplex filters 412, 414, 416 for filtering.

When the FDD/TDD RF receive signal comprises a TDD RF receive signal,the third switch 410 routes the TDD RF receive signal to an input of aselected one of the TDD receive filters 422, 424, 426 for filtering.Again, the at least one signal from the baseband subsystem controls theselection of the filters 412, 414, 416, 422, 424, 426 and the selectionis based at least in part on the arrangement of the paired spectrum 300.

The outputs of the TDD receive filters 422, 424, 426 and the receiverports of the FDD duplex filters 412, 414, 416 electrically connect to acorresponding one of the throws of the second switch 408. The secondswitch 408 routes the FDD/TDD RF receive signal to the receiver portionof the radio frequency device for further processing.

In the embodiment illustrated in FIG. 4, the second switch 410 comprisesa single pole 6 throw (SP6T) switch where three of the throwselectrically connect to an output of a corresponding TDD receive filter422, 424, 426, three of the throws electrically connect to acorresponding receiver port of the FDD duplex filters 412, 414, 416, andthe pole electrically connects to the receiver portion of the radiofrequency device. The position of the second switch 408 is controlled byat least one signal from the baseband subsystem that includes theprocessor. When the switching circuit 400 is configured to receive, thesecond switch 408 electrically connects a selected one of the outputs ofthe TDD receive filters 422, 424, 426 or antenna ports of the FDD duplexfilters 412, 414, 416 to the receiver portion of the radio frequencydevice. Again, the at least one signal from the baseband subsystemcontrols the selection of the filters 412, 414, 416, 422, 424, 426 andthe selection is based at least in part on the arrangement of the pairedspectrum 300.

FIG. 5 is a schematic diagram of another embodiment of a switchingcircuit 500 configured to implement both TDD and FDD in a shared band.The switching circuit 500 re-uses the transmit filters of the FDD duplexfilters to filter both FDD RF transmit signals and TDD RF transmitsignals.

As described above with respect to FIG. 4, the switching circuit 500receives the impedance matched FDD/TDD RF transmit signal from thematching circuit 404. The FDD/TDD RF transmit signal may be received asan FDD signal or a TDD signal, depending on the arrangement of thepaired spectrum 300. The switch 500 routes the FDD/TDD RF transmitsignal through the appropriate filter to the FDD/TDD antenna 450 for TDDtransmission or FDD transmission, depending on the arrangement of thepaired spectrum 300.

Further, the switching circuit 500 receives the FDD/TDD RF receivesignal from the FDD/TDD antenna 450 and routes the FDD/TDD RF receivesignal through the appropriate filter to the receiver portion of theradio frequency device for subsequent baseband processing. The FDD/TDDRF receive signal may be received as an FDD signal or a TDD signal,depending on the arrangement of the paired spectrum 300.

The switching circuit 500 comprises a first or TX select switch 506, asecond or RX select switch or 508, a third switch or antenna switchingmodule 510, a plurality of FDD duplex filters 512, 514, 516, and aplurality of TDD receive filters 522, 524, 526. The FDD duplex filters512, 514, 516 are configured to filter FDD RF transmit signals and TDDRF transmit signals from the matching circuit 404 and FDD RF receivesignals from the FDD/TDD antenna 450. In an embodiment, the transmit andreceive filters of the FDD duplex filters 512, 514, 516 comprisebandpass filters. The TDD receive filters 522, 524, 526 are configuredto filter TDD RF receive signals from the FDD/TDD antenna 450. In anembodiment, the TDD receive filters 522, 524, 526 comprise bandpassfilters.

In the example illustrated in FIG. 5, the plurality of FDD duplexfilters comprises three filters, and the plurality of TDD receivefilters comprises three filters. In other embodiments, there may be moreor less than three FDD duplex filters, and more or less than three TDDreceive filters, depending on the frequency band allocation for FDDsignals and the time slot allocation for TDD signals.

The first switch 506 receives the output of the matching circuit 404 androutes the FDD/TDD RF transmit signal to the transmitter port of theselected FDD duplex filter 512, 514, 516. In an embodiment, the TDD RFtransmit signals and the FDD RF transmit signals use the same orapproximately the same frequency bands such that the FDD duplex filters512, 514, 516 are configured to filter both the FDD RF transmit signaland the TDD RF transmit signal.

In the embodiment illustrated in FIG. 5, the first switch 506 comprisesa single pole 3 throw (SP3T) switch where the throws are electricallyconnected to the transmitter port of a corresponding one of the FDDduplex filters 512, 514, 516 and the pole electrically connects to theoutput of the matching circuit 404. The position of the first switch 506is controlled by at least one signal from the baseband subsystem and isbased at least in part on the arrangement of the paired spectrum 300.

The antenna ports of the FDD duplex filters 512, 514, 516 electricallyconnect to a corresponding one of the throws of the third switch 510.The third switch 510 routes the FDD/TDD RF transmit signal to theFDD/TDD antenna 450 for transmission.

In the embodiment illustrated in FIG. 5, the third switch 510 comprisesa single pole 6 throw (SP6T) switch where three of the throwselectrically connect to a corresponding antenna port of the FDD duplexfilters 512, 514, 516, three of the throws electrically connect to aninput of a corresponding TDD receive filter 522, 524, 526, and the poleelectrically connects to antenna circuitry including the FDD/TDD antenna450. The position of the third switch 510 is controlled by at least onesignal from the baseband subsystem that includes the processor. When theswitching circuit 500 is configured to transmit, the third switch 510 isconfigured to electrically connect a selected one of the antenna portsof the FDD duplex filters 512, 514, 516 to the FDD/TDD antenna 450.Again, the at least one signal from the baseband subsystem controls theselection of the FDD duplex filters 512, 514, 516 and the selection isbased at least in part on the arrangement of the paired spectrum 300.

When the switching circuit 500 is configured to receive, the FDD/TDDantenna 450 receives the FDD/TDD RF receive signal. The third switch 510routes the FDD/TDD RF receive signal to the appropriate receive filter.For example when the FDD/TDD RF receive signal comprises an FDD RFreceive signal, the third switch 510 routes the FDD RF receive signal tothe antenna port of the selected one of the FDD duplex filters 512, 514,516 for filtering. When the FDD/TDD RF receive signal comprises a TDD RFreceive signal, the third switch 510 routes the TDD RF receive signal toa selected one of the TDD receive filters 522, 524, 526 for filtering.

The outputs of the TDD receive filters 522, 524, 526 and the receiverports of the FDD duplex filters 512, 514, 516 electrically connect to acorresponding one of the throws of the second switch 508. The secondswitch 508 routes the FDD/TDD RF receive signal to the receiver portionof the radio frequency device for further processing.

In the embodiment illustrated in FIG. 5, the second switch 510 comprisesa single pole 6 throw (SP6T) switch where three of the throws areelectrically connected to an output of a corresponding TDD receivefilter 522, 524, 526, three of the throws electrically connect to acorresponding receiver port of the FDD duplex filters 512, 514, 516 andthe pole electrically connects to the receiver portion. The position ofthe second switch 508 is controlled by at least one signal from thebaseband subsystem that includes the processor and is based at least inpart on the arrangement of the paired spectrum 300. When the switchingcircuit 500 is receiving, the second switch 508 electrically connects aselected one of the outputs of the filters 512, 514, 516, 522, 524, 526to the receiver portion of the radio frequency device.

FIG. 6A is a schematic diagram of another embodiment of a switchingcircuit 600A configured to implement both TDD and FDD in a shared band.The switching circuit 600A re-uses the transmit filters of the FDDduplex filters to filter both FDD transmit RF signals and TDD RFtransmit signals, and re-uses the receive filters of the FDD duplexfilters to filter both FDD receive signals and TDD RF receive signals.

As described above with respect to FIG. 4, the switching circuit 600Areceives the impedance matched FDD/TDD RF transmit signal from thematching circuit 404. The switching circuit 600A routes the FDD/TDD RFtransmit signal through the appropriate filter to the FDD/TDD antenna450 for TDD transmission or FDD transmission, depending on thearrangement of the paired spectrum 300. Further, the switching circuit600A receives the RF receive signal from the FDD/TDD antenna 450 androutes the FDD/TDD RF receive signal through the appropriate filter tothe receive portion of the radio frequency device for subsequentbaseband processing. The FDD/TDD RF receive signal may be received as anFDD signal or a TDD signal, depending on the arrangement of the pairedspectrum 300.

The switching circuit 600A comprises a first or TX/RX select switch606A, a second or RX select switch or 608A, a third switch or antennaswitching module 610A, and a plurality of FDD duplex filters 612A, 614A,616A. The FDD duplex filters 612A, 614A, 616A are configured to filterTDD RF transmit signals and FDD RF transmit signals from the matchingcircuit 404. The FDD duplex filters 612A, 614A, 616A are furtherconfigured to filter TDD RF receive signals and FDD RF receive signalsfrom the FDD/TDD antenna 450. In an embodiment, the transmit filters andthe receive filters of the FDD duplex filters 612A, 614A, 616A comprisebandpass filters.

In the example illustrated in FIG. 6A, the plurality of FDD duplexfilters comprises three filters. In other embodiments, there may be moreor less than three FDD duplex filters, depending on the frequency bandallocation for FDD signals and the time slot allocation for TDD signals.

In the embodiment illustrated in FIG. 6A, the first switch 606Acomprises a double pole 3 throw (DP3T) switch where the throwselectrically connect to the transmitter port of a corresponding one ofthe FDD duplex filters 612A, 614A, 616A. A first pole of the firstswitch 606A electrically connects to the output of the matching circuit404 and a second pole of the first switch 606A electrically connects tothe second switch 608A.

When the switching circuit 600A is configured to transmit, the firstswitch 606A electrically connects the output of the matching circuit 404to the transmitter port of a selected one of the FDD duplex filters612A, 614A, 616A. In an embodiment, the TDD RF transmit signals and theFDD RF transmit signals use the same or approximately the same frequencybands such that the FDD duplex filters 612A, 614A, 616A are configuredto filter both the FDD RF transmit signal and the TDD RF transmitsignal.

The position of the first switch 606A is controlled by at least onesignal from the baseband subsystem and is based at least in part on thearrangement of the paired spectrum 300.

The antenna ports of the FDD duplex filters 612A, 614A, 616Aelectrically connect to a corresponding one of the throws of the thirdswitch 610A. The third switch 610A routes the FDD/TDD RF transmit signalto the FDD/TDD antenna 450 for transmission.

In the embodiment illustrated in FIG. 6A, the third switch 610Acomprises a single pole 3 throw (SP3T) switch where the three throwselectrically connect to the antenna port of a corresponding FDD duplexfilter 612A, 614A, 616A and the pole electrically connects to antennacircuitry including the FDD/TDD antenna 450. The position of the thirdswitch 610A is controlled by at least one signal from the basebandsubsystem that includes the processor and is based at least in part onthe arrangement of the paired spectrum 300. When the switching circuit600A configured to transmit, the third switch 610A electrically connectsa selected one of the antenna ports of the FDD duplex filters 612A,614A, 616A to the FDD/TDD antenna 450.

When the switching circuit 600A is configured to receive, the FDD/TDDantenna 450 receives the FDD/TDD RF receive signal. The third switch610A routes the FDD/TDD RF receive signal to the antenna port of theselected one of the FDD duplex filter 612A, 614A, 616A where the FDD/TDDRF receive signal is filtered. When the FDD/TDD RF receive signalcomprises an FDD/TDD RF receive signal, the receive filter of theselected one of the FDD duplex filter 612A, 614A, 616A filters theFDD/TDD RF receive signal and the selected one of the FDD duplex filters612A, 614A, 616A outputs the filtered FDD/TDD RF receive signal throughits receiver port.

The receiver ports of the FDD duplex filters 612A, 614A, 616Aelectrically connect to a corresponding one of the throws of the secondswitch 608A. The second switch 608A routes the FDD RF receive signal tothe receiver portion of the radio frequency device for furtherprocessing.

In the embodiment illustrated in FIG. 6A, the capability is furtherenhanced to enable the reception of signals within the transmit band ofthe duplex filters. The second switch 608A comprises a single pole 4throw (SP4T) switch where three of the throws electrically connect to acorresponding receiver port of the FDD duplex filters 612A, 614A, 616A,and additionally the fourth throw electrically connects to the secondpole of the first switch 606A, and the pole electrically connects to thereceiver portion. The position of the second switch 608A is controlledby at least one signal from the baseband subsystem that includes theprocessor and is based at least in part on the arrangement of the pairedspectrum 300. When the switching circuit 600A is configured to receiveFDD RF receive signals, the second switch 608A electrically connects thereceiver port of a selected one of the FDD duplex filters 612A, 614A,616A to the receive portion of the radio frequency device.

When the FDD/TDD RF receive signal comprises a desired TDD RF receivesignal that exists within the transmit band of one of the FDD duplexfilters 612A, 614A, 616A, the transmit filter of the selected one of theFDD duplex filter 612A, 614A, 616A filters the TDD RF receive signal andthe selected one of the FDD duplex filters 612A, 614A, 616A outputs thefiltered TDD RF receive signal through its transmitter port. In anembodiment, the TDD RF receive signals and the FDD RF transmit signalsuse the same or approximately the same frequency bands such that the FDDduplex filters 612A, 614A, 616A are configured to filter both the FDD RFtransmit signal and the TDD RF receive signal.

Further, when the FDD/TDD RF receive signal comprises a TDD RF receivesignal, the at least one control signal controls the first switch 606Ato electrically connect the second pole of the first switch to thetransmitter port of the selected one of the FDD duplex filters 612A,614A, 616A.

As described above, the second pole of the first switch 606A alsoelectrically connects to the fourth throw of the second switch 608A.Thus, when the FDD/TDD RF receive signal comprises a TDD RF receivesignal, the first switch 606A, the second switch 608A, and the thirdswitch 610A are configured such that the TDD RF receive signal is routedto the antenna port of the selected one of the FDD duplex filters 612A,614A, 616A, and filtered. The filtered TDD RF receive signal is outputthrough the transmitter port of the selected one of the FDD duplexfilters 612A, 614A, 616A through the second pole of the first switch606A and the fourth throw of the second switch 608A to the receiveportion of the radio frequency device for further processing.

FIG. 7 illustrates an example of a re-apportioned FDD RX DL band 702 forTDD application of an FDD paired spectrum 700. The FDD spectrum 700comprises the FDD TX UL+TDD TX/RX band 302 or band 302 and there-apportioned or re-farmed FDD receive downlink that supports TDDtransmit/receive use of the FDD receive band, indicated herein as FDD RXDL+TDD TX/RX 706 or band 706. Band 706 comprises one or more FDD RXbands 714, one or more dual-use bands 716, and one or more TDD RX/TDD TXbands 718.

The FDD RX bands 714 are used for FDD receive. For example, legacy userequipment uses the FDD RX bands 714 for continuous FDD receiving, justas FDD RX band 106 is used for continuous FDD receiving.

The TDD TX/RX band 718 is used for TDD transmit and receive. The TDDTX/RX band 718 is synchronized to enable sufficient receive performanceand to avoid nearby TDD transmitting.

In an embodiment, the TDD TX/RX band 718 can be placed adjacent to theFDD RX spectrum 714 as long as neighboring FDD user equipment does notcause desense or a degradation in sensitivity due to noise sources ofthe TDD user equipment.

Guard bands may enhance coexistence of the FDD RX spectrum and the TDDRX/TDD TX spectrum within the band 706 where nearby user equipment maybe interfering with the receiving. In an embodiment, the dual-use bands716 comprise guard bands. This can be dynamically allocated for spectralefficiency.

In another embodiment, the dual-use bands 716 may be used for TDDreceiving. In a further embodiment, the dual-use bands 716 may be usedfor reception when TDD receive is useful or needed, and simply as guardbands when receive operation is required and FDD receive interference ispresent. In an embodiment, the interference can be determined bymeasuring the received signal strength indication (RSSI). In anembodiment, the use of the dual-use bands 716 as either guard bands orTDD transmit is based at least in part on RSSI feedback. In anembodiment, the use of the dual-use bands 716 as either guard bands orTDD receive bands can be dynamically adjusted if RSSI feedback indicatesinterference. Guard bands 716 and PA linearity can be adjusted as neededto achieve sufficient performance.

In another embodiment, the FDD spectrum 700 comprises the FDD TX UL 102and the FDD RX DL+TDD TX/RX 706 or band 706, as described above.

FIG. 6B is a schematic diagram of another embodiment of a switchingcircuit 600B configured to implement both TDD and FDD in a shared band.The switching circuit 600B re-uses the receive filters of the FDD duplexfilters to filter both FDD receive RF signals and TDD RF receivesignals, and re-uses the receive filters of the FDD duplex filters tofilter the FDD receive signals, TDD RF receive signals, and TDD transmitsignals.

In the embodiment illustrated in FIG. 6B, the first switch 606Bcomprises a double pole 3 throw (DP3T) switch where the poles can beelectrically connected together and route the transmit signal to thesecond switch 608B.

When the FDD/TDD RF transmit signal comprises a desired TDD RF transmitsignal that exists within the receive band of one of the FDD duplexfilters 612B, 614B, 616B, the receive filter of the selected one of theFDD duplex filter 612B, 614B, 616B filters the TDD RF transmit signaland the selected one of the FDD duplex filters 612B, 614B, 616B outputsthe filtered TDD RF transmit signal through its antenna port. In anembodiment, the TDD RF transmit signals and the FDD RF receive signalsuse the same or approximately the same frequency bands such that the FDDduplex filters 612B, 614B, 616B are configured to filter both the FDD RFreceive signal, the TDD RF receive signal, and the TDD RF transmitsignal.

Further, when the FDD/TDD RF transmit signal comprises a TDD RF transmitsignal within one of the duplexer receive bands, the at least onecontrol signal controls the first switch 606B to electrically connectthe second pole of the first switch to the first pole of the firstswitch, and route the TDD transmit signal to the second pole of thesecond switch 608B. The second switch 608B is configured to connect itssecond pole to the desired receive filter of the appropriate duplexer612B, 614B, 616B, and then onto through to the antenna 450A. In this waythe transmit signal path is enabled to re-use the receive portion of theavailable duplexers.

FIG. 8 illustrates an example of a re-apportioned duplex gap band 804for TDD application of an FDD paired spectrum 800. In an embodiment, thepaired spectrum 800 comprises the FDD TX UL+TDD TX/RX band 302, the FDDRX UL band 106, and the re-apportioned duplex gap band 804. In anembodiment, the gap band 804 comprises one or more dual use bands 816,820 and one or more TDD RX/TDD TX bands 818. The TDD RX/TDD TX band 818is used for TDD transmit and receive and is synchronized to enablesufficient receive performance and to avoid nearby TDD transmit.

Guard bands may enhance coexistence of the FDD paired spectrum 800 andthe TDD RX/TDD TX band 818 within the gap band 804. In an embodiment,the dual-use bands 816, 820 comprise guard bands. This can bedynamically allocated for spectral efficiency.

In another embodiment, the dual-use band 816 may be used for TDDtransmit. In a further embodiment, the dual-use band 816 may be used fortransmit when TDD transmit is useful or needed, and simply as a guardband when interference is present. In an embodiment, the interferencecan be determined by measuring the received signal strength indication(RSSI). In an embodiment, the use of the dual-use band 816 as either theguard bands or TDD transmit is based at least in part on RSSI feedback.In an embodiment, the use of the dual-use band 816 as either the guardband or a TDD transmit band can be dynamically adjusted if RSSI feedbackindicates interference. Guard band 816 and PA linearity can be adjustedas needed to achieve sufficient performance.

In another embodiment, the dual-use band 820 may be used for TDDreception. In a further embodiment, the dual-use band 820 may be usedfor reception when TDD receive is useful or needed, and simply as guardbands interference is present. In an embodiment, the interference can bedetermined by measuring the received signal strength indication (RSSI).In an embodiment, the use of the dual-use band 820 as either a guardband or a TDD receive is based at least in part on RSSI feedback. In anembodiment, the use of the dual-use band 820 as either a guard band or aTDD receive band can be dynamically adjusted if RSSI feedback indicatesinterference. Guard band 820 and PA linearity can be adjusted as neededto achieve sufficient performance.

In another embodiment, the FDD spectrum 800 comprises the gap band 804,one of the FDD TX UL band 102 and the FDD TX UL+TDD TX/RX band 302, andone of the FDD RX DL band 106 and the FDD RX DL+TDD TX/RX band 706.

FIG. 6C is a schematic diagram of another embodiment of a switchingcircuit 600C configured to implement both TDD and FDD in a shared band.The switching circuit 600C is configured to switch the RF transmitsignal and the RF receive signal for use in a re-allocated FDD TX uplinkband 302 as described above with respect to FIG. 6A. The switchingcircuit 600C is further configured to switch the TDD transmit signal andthe TDD receive signal for a re-apportioned duplex gap band 804 of anFDD paired spectrum for TDD application, where, in an embodiment, no FDDfiltering exists.

In an embodiment, the switching circuit 600C comprises the switchingcircuit 600A including the FDD duplexer filters 612A, 614A, 616A and theRX select switch 608A with an additional signal path between the TX/RXselect switch 606A and the antenna switching module 610A comprising aTDD duplex gap filter 618C. The TDD duplex gap filter 618C filters theTDD transmit and TDD receive signals in the re-apportioned duplex gapband 804.

To accommodate the additional switching path a first or TX/RX selectswitch 606C comprises a double pole 4 throw (DP4T) switch where the DP3Tportion of the TX/RX select switch 606C operates as the TX/RX selectswitch 606A and is described above with respect to FIG. 6A. The fourththrow of the TX/RX select switch 606C electrically connects to a firstport of the TDD duplex gap filter 618D.

To further accommodate the additional switching path a third switch orantenna switching module 610C comprises a single pole 4 throw (SP4T)switch where the SP3T portion of the antenna switching module 610Coperates as the antenna switching module 610A and is described abovewith respect to FIG. 6A. The fourth throw of the antenna-switchingmodule 610C electrically connects to a second port of the TDD duplex gapfilter 618C.

The positions of the switches 606C, 608A, and 610C are controlled by atleast one signal from the baseband subsystem that includes the processorand is based at least in part on the arrangement of the paired spectrum300, 800.

When the switching circuit 600C is configured to transmit TDD signals inthe re-allocated duplex gap 804, the TX/RX select switch 606Celectrically connects the output of the matching circuit 604 to thefirst port of the duplex gap TDD filter 618C. The duplex gap TDD filter618C filters the TDD transmit signal. In an embodiment, the duplex gapTDD filter 618C comprises a bandpass filter. The antenna-switchingmodule 610C receives the filtered TDD signal and electrically connectsto antenna circuitry including the FDD/TDD antenna 450.

When the switching circuit 600C is configured to receive TDD signals inthe re-allocated duplex gap 804, the antenna switching module 610Celectrically connects the TDD receive signal to the second port of theduplex gap TDD filter 618C, where the duplex gap TDD filter 618C filtersthe TDD receive signal. The TX/RX select switch 606C receives thefiltered TDD receive signal and electrically connects through the secondpole the TX/RX select switch 606C to the RX select switch 608A. The RXselect switch 608A routes the TDD RF receive signal to the receiverportion of the radio frequency device for further processing.

FIG. 6D is a schematic diagram of another embodiment of a switchingcircuit 600D configured to implement both TDD and FDD in a shared band.The switching circuit 600D is configured to switch the RF transmitsignal and the RF receive signal for use in a re-allocated FDD RXdownlink band 706 as described above with respect to FIG. 6B. Theswitching circuit 600D is further configured to switch the TDD transmitsignal and the TDD receive signal for a re-apportioned duplex gap band804 of an FDD paired spectrum for TDD application, where, in anembodiment, no FDD filtering exists.

In an embodiment, the switching circuit 600D comprises the switchingcircuit 600B including the FDD duplexer filters 612B, 614B, 616B and theRX select switch 608B with an additional signal path between the TX/RXselect switch 606B and the antenna switching module 610B comprising aTDD duplex gap filter 618D. The TDD duplex gap filter 618D filters theTDD transmit and TDD receive signals in the re-apportioned duplex gapband 804.

To accommodate the additional switching path a first or TX/RX selectswitch 606D comprises a double pole 4 throw (DP4T) switch where the DP3Tportion of the TX/RX select switch 606D operates as the TX/RX selectswitch 606B and is described above with respect to FIG. 6B. The fourththrow of the TX/RX select switch 606D electrically connects to a firstport of the TDD duplex gap filter 618D. To further accommodate theadditional switching path a third switch or antenna switching module610D comprises a single pole 4 throw (SP4T) switch where the SP3Tportion of the antenna switching module 610D operates as the antennaswitching module 610B and is described above with respect to FIG. 6B.The fourth throw of the antenna-switching module 610D electricallyconnects to a second port of the TDD duplex gap filter 618D.

The positions of the switches 606D, 608B, and 610D are controlled by atleast one signal from the baseband subsystem that includes the processorand is based at least in part on the arrangement of the paired spectrum700, 800.

When the switching circuit 600D is configured to transmit TDD signals inthe re-allocated duplex gap 804, the TX/RX select switch 606Delectrically connects the output of the matching circuit 604 to thefirst port of the duplex gap TDD filter 618D. The duplex gap TDD filter618D filters the TDD transmit signal. In an embodiment, the duplex gapTDD filter 618D comprises a bandpass filter. The antenna-switchingmodule 610D receives the filtered TDD signal and electrically connectsto antenna circuitry including the FDD/TDD antenna 450.

When the switching circuit 600D is configured to receive TDD signals inthe re-allocated duplex gap 804, the antenna switching module 610Delectrically connects the TDD receive signal to the second port of theduplex gap TDD filter 618D, where the duplex gap TDD filter 618D filtersthe TDD receive signal. The TX/RX select switch 606D receives thefiltered TDD receive signal and electrically connects through the secondpole the TX/RX select switch 606D to the RX select switch 608B. The RXselect switch 608B routes the TDD RF receive signal to the receiverportion of the radio frequency device for further processing.

In another embodiment, the additional signal path comprising the TDDduplex gap filter 618D for the switching circuit 600D is between theTX/RX select switch 606D and the RX select switch 608B.

In an embodiment, the various filter segments 612A, 614A, 616A,618C/612B, 614B, 616B, 618D overlap by at least a minimum channelbandwidth, such that a 15 MHz channel, for example, can be transmittedanywhere on a 100 kHz grid within the band of interest.

The switching circuits 400, 500, 600 are described as examples ofswitching circuits to implement a shared FDD and TDD spectrum. In otherembodiments, the switches 406, 408, 410, 506, 508, 510, 606, 608, 610may have more or less poles and throws, depending on the arrangement ofthe spectrum 300, 700, 800.

FIG. 9A is an exemplary block diagram of a multimode semiconductor die900 including the switching and signal filtering circuit 400, 500, 600Aor 600B that includes a filtering circuit 902 and a switching circuit904. In one embodiment, the multimode semiconductor die 900 comprisesthe switching and signal filtering circuit 400; the filtering circuit902 comprises the filters 412, 414, 416, 422, 424, 426, 432, 434, 436;and the switching circuit 904 comprises the switches 406, 408, and 410.In another embodiment, multimode semiconductor die 900 comprises theswitching and signal filtering circuit 500; the filtering circuit 902comprises the filters 512, 514, 516, 522, 524, 526; and the switchingcircuit 904 comprises the switches 506, 508, 510. In a furtherembodiment, the multimode semiconductor die 900 comprises the switchingand signal filtering circuit 600A; the filtering circuit 902 comprisesthe filters 612A, 614A, 616A; and the switching circuit 904 comprisesthe switches 606A, 608A, 610A. In a further embodiment, the multimodesemiconductor die 900 comprises the switching and signal filteringcircuit 600B; the filtering circuit 902 comprises the filters 612B,614B, 616B; and the switching circuit 904 comprises the switches 606B,608B, 610B.

FIG. 9B is an exemplary block diagram of a set of semiconductor diecomprising a first semiconductor die 910 including a filtering circuit912 and a second semiconductor die 920 including a switching circuit924. In an embodiment, the die set comprises the switching and signalfiltering circuit 400; the filtering circuit 912 comprises the filters412, 414, 416, 422, 424, 426, 432, 434, 436; and the switching circuit924 comprises the switches 406, 408, and 410. In another embodiment, thedie set comprises the switching and signal filtering circuit 500; thefiltering circuit 912 comprises the filters 512, 514, 516, 522, 524,526; and the switching circuit 924 comprises the switches 506, 508, 510.In a further embodiment, the die set comprises the switching and signalfiltering circuit 600A; the filtering circuit 912 comprises the filters612A, 614A, 616A; and the switching circuit 924 comprises the switches606A, 608A, 610A. In a further embodiment, the die set comprises theswitching and signal filtering circuit 600B; the filtering circuit 912comprises the filters 612B, 614B, 616B; and the switching circuit 924comprises the switches 606B, 608B, 610B.

In an embodiment, the semiconductor die 900, 910, 920 comprises asilicon (Si) die and assorted filters. In an embodiment, thesemiconductor die 900 comprises a silicon-on-Insulator (SOI) die andassorted filters. In another embodiment, the die 900, 910, 920 cancomprise a gallium arsenide (GaAs) die, a pseudomorphic high electronmobility transistor (pHEMT) die, or the like. In another embodiment, thefilter content can comprise any variety of acoustic filter technologiessuch as surface acoustic wave (SAW), film bulk acoustic resonator(FBAR), bulk acoustic wave (BAW), and the like, reactive components suchas inductors and capacitors, and/or other ceramic/cavity resonatortopologies and technologies.

FIG. 9C is an exemplary perspective cut-away view of an embodiment of asurface acoustic wave (SAW) filter 930. SAW devices utilize thepiezoelectric effect to convert energy back and forth between theelectrical and mechanical realms where the presence of an electricalfield causes the material to deform and the application of a mechanicalstress induces an electric charge. The SAW filter 930 is illustrated asa wafer level packaged device and comprises a metal lid 932, a solderseal-ring 934, and a plated wall 936 configured for hermetic wafer levelpackaging. The SAW filter 930 further comprises a plurality ofthrough-wafer via 938 and a plurality of solder pads 940 configured toprovide electrical connections. In an embodiment, each filter 412, 414,416, 422, 424, 426, 432, 434, 436, 512, 514, 516, 522, 524, 526, 612A,614A, 616A, 612B, 614B, 616 b can comprise the SAW filter 930. Inanother embodiment, each filter 412, 414, 416, 422, 424, 426, 432, 434,436, 512, 514, 516, 522, 524, 526, 612A, 614A, 616A, 612B, 614B, 616Bcan be packaged separately as a SAW filter and assembled onto amulti-chip module that includes the switching semiconductor die 920. Ina further embodiment, each filter 412, 414, 416, 422, 424, 426, 432,434, 436, 512, 514, 516, 522, 524, 526, 612A, 614A, 616A, 612B, 614B,616B can be packaged as a separate part built from piezoelectricmaterial and metal interconnect technology and then assembled onto amulti-chip module alongside the switching die 920, which can be a Si orSOI semiconductor die.

FIG. 10A is an exemplary block diagram of switching module 1000including the multimode semiconductor die 900 of FIG. 9A. FIG. 10B is anexemplary block diagram of a multi-chip switching module 1010 includingthe filtering semiconductor die 910 and the switching semiconductor die920 of FIG. 9B.

FIG. 10C is an exemplary block diagram of a multi-chip switching module1030 including the switching semiconductor die 920 and a plurality ofSAW filters 930. In an embodiment, the multi-chip module 1030 furtherincludes power amplifier (PA) circuitry 1008.

The modules 1000, 1010, 1030 further include connectivity 1002 toprovide signal interconnections, packaging 1004, such as for example, apackage substrate, for packaging of the circuitry, and other circuitrydie 1006, such as, for example amplifiers, pre-filters, post filtersmodulators, demodulators, down converters, and the like, as would beknown to one of skill in the art of semiconductor and multi-chip modulefabrication in view of the disclosure herein.

FIG. 11 is an exemplary block diagram illustrating a simplified wirelessdevice 1100 including an embodiment of the switching and signalconditioning/filtering circuit 400, 500, 600A or 600B configured toswitch and condition/filter the RF transmit signal and the RF receivesignal in order to implement both FDD and TDD in a shared band.

The wireless device 1100 includes a speaker 1102, a display 1104, akeyboard 1106, and a microphone 1108, all connected to a basebandsubsystem 1110. A power source 1142, which may be a direct current (DC)battery or other power source, is also connected to the basebandsubsystem 1110 to provide power to the wireless device 1100. In aparticular embodiment, the wireless device 1100 can be, for example butnot limited to, a portable telecommunication device such as a mobilecellular-type telephone. The speaker 1102 and the display 1104 receivesignals from baseband subsystem 1110, as known to those skilled in theart. Similarly, the keyboard 1106 and the microphone 1108 supply signalsto the baseband subsystem 1110. The baseband subsystem 1110 includes amicroprocessor (μP) 1120, memory 1122, analog circuitry 1124, and adigital signal processor (DSP) 1126 in communication via bus 1128. Bus1128, although shown as a single bus, may be implemented using multiplebusses connected as necessary among the subsystems within the basebandsubsystem 1110. The baseband subsystem 1110 may also include one or moreof an application specific integrated circuit (ASIC) 1132 and a fieldprogrammable gate array (FPGA) 1130.

The microprocessor 1120 and memory 1122 provide the signal timing,processing, and storage functions for wireless device 1100. The analogcircuitry 1124 provides the analog processing functions for the signalswithin baseband subsystem 1110. The baseband subsystem 1110 providescontrol signals to a transmitter 1150, a receiver 1170, a poweramplifier 1180, and a switching module 1190, for example.

It should be noted that, for simplicity, only the basic components ofthe wireless device 1100 are illustrated herein. The control signalsprovided by the baseband subsystem 1110 control the various componentswithin the wireless device 1100. Further, the function of thetransmitter 1150 and the receiver 1170 may be integrated into atransceiver.

The baseband subsystem 1110 also includes an analog-to-digital converter(ADC) 1134 and digital-to-analog converters (DACs) 1136 and 1138. Inthis example, the DAC 1136 generates in-phase (I) and quadrature-phase(Q) signals 1140 that are applied to a modulator 1152. The ADC 1134, theDAC 1136, and the DAC 1138 also communicate with the microprocessor1120, the memory 1122, the analog circuitry 1124, and the DSP 1126 viabus 1128. The DAC 1136 converts the digital communication informationwithin baseband subsystem 1110 into an analog signal for transmission tothe modulator 1152 via connection 1140. Connection 1140, while shown astwo directed arrows, includes the information that is to be transmittedby the transmitter 1150 after conversion from the digital domain to theanalog domain.

The transmitter 1150 includes the modulator 1152, which modulates theanalog information on connection 1140 and provides a modulated signal toupconverter 1154. The upconverter 1154 transforms the modulated signalto an appropriate transmit frequency and provides the upconverted signalto the power amplifier 1180. The power amplifier 1180 amplifies thesignal to an appropriate power level for the system in which thewireless device 1100 is designed to operate.

Details of the modulator 1152 and the upconverter 1154 have beenomitted, as they will be understood by those skilled in the art. Forexample, the data on connection 1140 is generally formatted by thebaseband subsystem 1110 into in-phase (I) and quadrature (Q) components.The I and Q components may take different forms and be formatteddifferently depending upon the communication standard being employed.

The power amplifier 1180 supplies the amplified signal to a front-endmodule 1162, where the amplified signal is conditioned and filtered byone or more signal conditioning filters for transmission. The front endmodule 1162 comprises an antenna system interface that may include, forexample, the switching module 1190 comprising an embodiment of theswitching and signal filtering circuit 400, 500, 600, or 600A configuredto switch a signal between the antenna 1160, the receiver 1170, and thepower amplifier 1180 (receiving the RF transmit signal from thetransmitter 1150), as described herein to implement FDD and TDD in ashared band. In an embodiment, the PA circuitry 1008 comprises the poweramplifier 1180. The RF transmit signal is supplied from the front-endmodule 1162 to the antenna 1160. In an embodiment, the antenna 1160comprises an FDD/TDD antenna.

In an embodiment, the front-end module 1162 comprises the switchingmodule 1190. In an embodiment, switching module 1190 comprises theswitching module 1000 including the semiconductor die 900. In anotherembodiment, switching module 1190 comprises the switching module 1010including the filtering semiconductor die 910 and the switchingsemiconductor die 920. In a further embodiment, the switching module1190 comprises the multi-chip module 1030 including one or more SAWfilters 930 and the switching semiconductor die 920. In theseembodiments, the switching module 1190 comprises an embodiment of theswitching and signal filtering circuit 400, 500, 600A, or 600B.

A signal received by antenna 1160 will be directed from the front-endmodule 1162 to the receiver 1170. The receiver 1170 includes low noiseamplifier circuitry 1172, a downconverter 1174, a filter 1176, and ademodulator 1178.

If implemented using a direct conversion receiver (DCR), thedownconverter 1174 converts the amplified received signal from an RFlevel to a baseband level (DC), or a near-baseband level (approximately100 kHz). Alternatively, the amplified received RF signal may bedownconverted to an intermediate frequency (IF) signal, depending on theapplication. The downconverted signal is sent to the filter 1176. Thefilter 1176 comprises a least one filter stage to filter the receiveddownconverted signal as known in the art.

The filtered signal is sent from the filter 1176 to the demodulator1178. The demodulator 1178 recovers the transmitted analog informationand supplies a signal representing this information via connection 1186to the ADC 1134. The ADC 1134 converts these analog signals to a digitalsignal at baseband frequency and transfers the signal via bus 1128 tothe DSP 1126 for further processing.

Terminology

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense, as opposed to anexclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to.” The words “coupled” or connected”, asgenerally used herein, refer to two or more elements that may be eitherdirectly connected, or connected by way of one or more intermediateelements. Additionally, the words “herein,” “above,” “below,” and wordsof similar import, when used in this application, shall refer to thisapplication as a whole and not to any particular portions of thisapplication. Where the context permits, words in the above DetailedDescription using the singular or plural number may also include theplural or singular number respectively. The word “or” in reference to alist of two or more items, that word covers all of the followinginterpretations of the word: any of the items in the list, all of theitems in the list, and any combination of the items in the list.

Moreover, conditional language used herein, such as, among others,“can,” “could,” “might,” “may,” “e.g.,” “for example,” “such as” and thelike, unless specifically stated otherwise, or otherwise understoodwithin the context as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements and/or states. Thus, such conditional language is notgenerally intended to imply that features, elements and/or states are inany way required for one or more embodiments or that one or moreembodiments necessarily include logic for deciding, with or withoutauthor input or prompting, whether these features, elements and/orstates are included or are to be performed in any particular embodiment.

The above detailed description of certain embodiments is not intended tobe exhaustive or to limit the invention to the precise form disclosedabove. While specific embodiments of, and examples for, the inventionare described above for illustrative purposes, various equivalentmodifications are possible within the scope of the invention, as thoseordinary skilled in the relevant art will recognize in view of thedisclosure herein.

For example, while processes or blocks are presented in a given order,alternative embodiments may perform routines having steps, or employsystems having blocks, in a different order, and some processes orblocks may be deleted, moved, added, subdivided, combined, and/ormodified. Each of these processes or blocks may be implemented in avariety of different ways. In addition, while processes or blocks are attimes shown as being performed in series, these processes or blocks mayinstead be performed in parallel, or may be performed at differenttimes.

The teachings of the invention provided herein can be applied to othersystems, not necessarily the systems described above. The elements andacts of the various embodiments described above can be combined toprovide further embodiments.

While certain embodiments of the inventions have been described, theseembodiments have been presented by way of example only, and are notintended to limit the scope of the disclosure. Indeed, the novel methodsand systems described herein may be embodied in a variety of otherforms; furthermore, various omissions, substitutions, and changes in theform of the methods and systems described herein may be made withoutdeparting from the spirit of the disclosure. The accompanying claims andtheir equivalents are intended to cover such forms or modifications aswould fall within the scope and spirit of the disclosure.

What is claimed is:
 1. A switching circuit for use in a frequencydivision duplex (FDD) spectrum re-allocated for time division duplex(TDD) application, the switching circuit comprising: a first filterconfigured to filter a TDD receive signal; a duplex filter configured tofilter an FDD receive signal; and a plurality of switches configured toroute the FDD receive signal from an antenna through the duplex filterto receiver circuitry and to route the TDD receive signal from theantenna through the first filter to the receiver circuitry, the FDD andTDD receive signals sharing the FDD spectrum.
 2. The switching circuitof claim 1 wherein the duplex filter includes a surface acoustic wave(SAW) filter.
 3. The switching circuit of claim 1 further comprising asecond filter configured to filter a TDD transmit signal, the duplexfilter further configured to filter an FDD transmit signal.
 4. Theswitching circuit of claim 3 wherein the first filter, the secondfilter, and the duplex filter include bandpass filters.
 5. The switchingcircuit of claim 3 wherein the plurality of switches are furtherconfigured to route the TDD transmit signal from transmitter circuitrythrough the second filter to the antenna, and to route the FDD transmitsignal from the transmitter circuitry through the duplex filter to theantenna, the FDD and TDD transmit signals sharing a first frequency bandof the FDD spectrum.
 6. The switching circuit of claim 5 wherein the TDDtransmit, TDD receive, FDD transmit, and FDD receive signals are radiofrequency (RF) signals.
 7. A wireless device including the switchingcircuit of claim
 1. 8. A switching module for use in a frequencydivision duplex (FDD) spectrum re-allocated for time division duplex(TDD) application, the switching module comprising: a switching circuitimplemented in a first semiconductor die, the switching circuitincluding a first filter configured to filter a TDD receive signal, aduplex filter configured to filter an FDD receive signal, and aplurality of switches configured to route the FDD receive signal from anantenna through the duplex filter to receiver circuitry and to route theTDD receive signal from the antenna through the first filter to thereceiver circuitry, the FDD and TDD receive signals sharing the FDDspectrum; and at least one of a prefilter circuit, a post filtercircuit, a power amplifier circuit, a switch circuit, a down convertercircuit, and a modulator circuit implemented in a second semiconductordie.
 9. The switching module of claim 8 wherein the duplex filterincludes a surface acoustic wave (SAW) filter.
 10. The switching moduleof claim 8 wherein the switching circuit further includes a secondfilter configured to filter a TDD transmit signal, the duplex filterfurther configured to filter an FDD transmit signal.
 11. The switchingmodule of claim 10 wherein the first filter, the second filter, and theduplex filter include bandpass filters.
 12. The switching module ofclaim 10 wherein the plurality of switches are further configured toroute the TDD transmit signal from transmitter circuitry through thesecond filter to the antenna and to route the FDD transmit signal fromthe transmitter circuitry through the duplex filter to the antenna, theFDD and TDD transmit signals sharing a first frequency band of the FDDspectrum.
 13. The switching module of claim 8 wherein the duplex filterincludes a film bulk acoustic resonator (FBAR) filter.
 14. The switchingmodule of claim 8 wherein the duplex filter includes a bulk acousticwave (BAW) filter.
 15. A wireless device including the switching moduleof claim
 8. 16. A method to transmit and receive frequency divisionduplex (FDD) signals and time division duplex (TDD) signals in an FDDand TDD shared frequency band, the method comprising: routing an FDDreceive signal from an antenna to receiver circuitry through a duplexfilter configured to filter the FDD receive signal; and routing a TDDreceive signal from the antenna to the receiver circuitry through afirst filter configured to filter the TDD receive signal, the FDD andTDD receive signals sharing an FDD spectrum.
 17. The method of claim 16wherein the duplex filter includes a surface acoustic wave (SAW) filter.18. The method of claim 16 further comprising routing an FDD transmitsignal from the transmitter circuitry to the antenna through the duplexfilter further configured to filter the FDD transmit signal.
 19. Themethod of claim 18 further comprising routing a TDD transmit signal fromthe transmitter circuitry to the antenna through a second filterconfigured to filter the TDD transmit signal, the FDD and TDD transmitsignals sharing the FDD spectrum.
 20. The method of claim 19 wherein theduplex filter is selected from the group consisting of a surfaceacoustic wave (SAW) filter, a film bulk acoustic resonator (FBAR)filter, and a bulk acoustic wave (BAW) filter.